With a spread of information terminals, flat panel displays have been increasingly demanded as displays for computers. Furthermore, with the progress of information technology, information which was provided by paper media is increasingly computerized, and electronic paper or digital paper have been increasingly demanded as display media for mobile devices which are thin, lightweight and easily portable (see, e.g., Patent Document 1).
Generally, in a flat panel display, a display medium is formed using a device utilizing liquid crystals, organic electroluminescence (organic EL), electrophoresis, and the like. In such display media, technology with an active matrix device (thin-film transistor (TFT) device) as an image driving element is primarily used to ensure uniformity of screen brightness and a high frame rate. For example, in a conventional computer display, TFT devices are formed on the surface; and liquid crystals, organic EL devices, and the like are encapsulated.
The TFT devices may be primarily made of semiconductor such as amorphous silicon (a-Si) and polysilicon (p-Si). Such Si semiconductor devices (including metal films as necessary) are stacked to be a multilayer; and source, drain, and gate electrodes are sequentially formed on a substrate to manufacture a TFT device.
Formation of a TFT device made of such a Si material includes a high-temperature process, and thus, a substrate is limited to a material resistant to the process temperature. Therefore, in practice, the substrate needs to be made of a material with excellent thermal resistance, e.g., a glass substrate. Note that a quartz substrate may also be used, but it is expensive and causes cost problems when increasing the size of the display. Therefore, a glass substrate is generally used as the substrate on which a TFT device is formed.
However, a thin display formed by using a glass substrate is heavy and less flexible, and thus, may be damaged by impact of falling. This is undesirable when trying to meet demands for thin portable displays in accordance with the progress of the information technology.
In order to satisfy the demands for lightweight and thin displays, semiconductor devices (flexible semiconductor devices) including TFT devices on resin substrates (plastic substrates) have been developed in terms of increasing flexibility of the substrates and reducing the weight.
For example, Patent Document 2 teaches manufacturing a TFT device on a support member (e.g., glass substrate) by a process substantially the same as a conventional process, removing the TFT device from the glass substrate, and transferring the TFT device onto a resin substrate.
Patent Document 3 teaches directly forming a TFT device on a resin substrate.